Blood blisters are small fluid-filled sores, which usually appear on or around the lips. They usually appear shortly after colds and other illnesses. They are caused by the herpes simplex virus. They are often called cold sores, and affect 60-80% of Americans. They are also the most common manifestation of the herpes virus.

The first outbreak of blood blister is almost always more painful than recurrent outbreaks. The first time you get cold sores, they will usually be inside your mouth – usually on the gums, tongue or throat. Usually the outbreak is accompanied by fever (hence the name), swollen lymph nodes, and difficulty swallowing. Usually these outbreaks resolve themselves within a week, but treatment is recommended if it lasts longer than that.

Once a person has already been exposed to the herpes simplex virus, the virus lives in specific cells of the body. The virus can reactivate at any time, but usually a trigger is required. Skin trauma, stress, menstruation, sun exposure and fever are all common triggers. When the virus is reactivated, small sores will appear on and around the lips. At first, the blood blister will appear only as small red or white dots, and will slowly develop over the next 3-5 days. They will become filled with fluid, and eventually crust over. Outbreaks are not extremely common, but most people report having about 2 outbreaks per year.

Before blisters actually form, you can usually feel them coming. This is because prodromes, or symptoms before the main outbreak, are common with herpes. Usually people will feel tingling, burning or general pain in the area around the mouth. These prodomes can last anywhere from 2 hours to 2 days. Ideally, treatment should be started as soon as symptoms start to worsen.

If you are not sure if you have blisters or not, you can usually make sure by observing them over 8-12 days. It usually takes about that long for a cold sore to run its course. It will start as a prodome, which is identified by tingling sensations. Next, it will blister and fill with fluid. Blisters usually form small clusters, and are very small in size. After that, blisters will usually rupture 1-3 days after they form. This results in a shallow red ulceration which eventually turns gray. This is usually the most painful stage, and also the stage when the sores are most contagious. After they rupture, the cold sores will usually crust over. Sores will usually be itchy and irritable in this stage, and if the skin gets too dry the scabs can crack, causing bleeding. If this happens, try to keep your skin as moist as possible by using Vaseline or another moisturizer. Usually cold sores take a while to heal, and often 2-4 scabs will develop and peel off one by one before a sore is fully healed. This can be a tedious process, but it’s best to let your sores heal on their own, and not bother them.